In order to study the interaction of neurotensin containing neurons with other neuronal systems, the neurotensin content of various rat brain regions was studied after haloperidol treatment and various brain lesions. Brain lesion experiments suggest that the neurotensin content of nucleus accumbens is probably located in intrinsic or short axon neurons projecting from stria terminalis. This neurotensin store increases 16 hrs after a single injection of haloperidol (2 mg/kg i.p.) and the increase was more pronounced after repeated injections of haloperidol (2 mg/kg i.p. per day for 2 weeks). The effect of haloperidol was not observed in preoptic area, hypothalamus, septum and amygdala. The specific effect of haloperidol suggests that neurotensin metabolism in nucleus accumbens may be modulated directly or indirectly through dopaminergic synapses.